The invention relates to mixed oxide catalysts and to their use for the catalytic gas phase oxidation of alkanes or mixtures of alkanes and olefins and to processes for preparing the catalysts.
In particular, the catalyst can be used to convert propane to acrolein and acrylic acid or isobutane to methacrolein and methacrylic acid, acrolein or methacrolein being formed at least as the main product. As well as the desired acrolein and acrylic acid product, the reaction of the alkane over heterogeneous catalysts with an oxygen-containing gas leads to a series of by-products: for example to the formation of CO2 and CO.
It is known that the type of chemical composition of the mixed oxide (phase formation and formation of reaction sites) and also the type of physical structure (for example porosity, surface size, form of the catalyst) and the type of heat removal can greatly influence the ability to form product (selectivity) and the productivity (space-time yield). In the case of alkane oxidation, the catalyst used is generally mixed oxides which, in their chemical and physical makeup, have a complex structure.